Wresting a forecast from chaos

GRAND JUNCTION – Throughout history, weather has defeated humanity’s best minds. Aristotle, otherwise an acknowledged genius, decided that lightning bolts happen when great quantities of “exhalation” are “squeezed out of the cloud.”

While our species has mapped the human genome, traveled to the moon and cloned sheep, we still have trouble figuring out the whether it’s going to snow tomorrow.

“Forecasting has gotten unbelievably more accurate as computing power has increased in the last decades. But even these days, we don’t get it right all the time,” said Jim Pringle, warning coordination meteorologist at the National Weather Service in Grand Junction.

There, the forecasters do much of their work in a room reminiscent of the Bridge on the Enterprise in “Star Trek”: screens everywhere, with experts from different galactic species comparing electric green squiggles to slightly larger electric pink squiggles.

This week, Pringle sat in his chair, like an earth-bound Captain Jean-Luc Picard, while Ellen Heffernan, a forecaster, jumped between four computer monitors, presenting the seven-day forecast.

“The green lines are active lines, and kind of indicate some areas of active weather,” she said. “But we have disagreement in the models.”

The forecasters debated what to do: side with the American model, which has recently struggled with predicting weather in the Southwest, or go with the European model, which has shown itself more adept at predicting storms in Colorado.

“These are big discrepancies. Stay tuned,” Pringle said.

The station

At the Weather Service in Grand Junction, 22 people are responsible for generating seven days worth of hourly weather predictions 52,000 square miles, stretching from Durango to Utah and up to the Wyoming border. The region is divided into 50,000 distinct grid spaces; each receives a forecast for surface wind speed, temperature, sky coverage, chance of precipitation, relative humidity and more.

The National Weather Service started under President Ulysess S. Grant in 1870 under the Department of War. Predicting the weather is clearly in America’s national interest: Vital to civilization, it determines our transport, our harvests and our moods. Predicting it correctly can trip the margin between life and death. This is especially true in rural Colorado, where residents incessantly discuss the probability of rain, the dangers of icy roads and the tyranny of wind.

When Pringle started at the National Weather Service 37 years ago, its forecasters were mostly former soldiers, who liked the work’s precision and were used to battling a dangerous enemy.

Now, he said, forecasters are mostly wonks with advanced degrees in math or meteorology. Their academic training is necessary because weather is based on chaos theory, meaning weather is nonlinear: it isn’t based on arithmetic, but exponents, so even small rounding errors can mean the difference between a sunny day in Palm Beach and a freak blizzard in Tallahassee. They sift through millions of data points gathered by volunteers, radars and geo-satellite tracking.

Thanks to them, and computers, weather predictions are infinitely more accurate than they were 30 years ago. Pringle noted forecasters’ reliably deft predictions of hurricanes’ courses, mudslides and tornados and pointed to the Silverton Center for Snow and Avalanche Studies.

Pringle is philosophical about laymen’s wisdom, saying that a friend of his who suffers from “really bad arthritis” can always tell when a storm is brewing, “when it’s coming and how bad it’s going to be, because of how fast the pressure is dropping in his joints.”

But the pressure on the forecasters can be great: Their profession’s mistakes are public in a way that doctors’ and lawyers’ aren’t. Forecaster Joe Ramey said forecasters constantly compare their predictions to what actually happened and adjust the weight their models place on certain variables. But even the most sophisticated models are regularly felled by the mathematical nuances of microclimates: The same storm will hit Durango differently than it hits Cortez.

Ramey said inaccurate forecasts are easy for laymen to deride.

“When we predict no rain and snow for D.C., but they get 6 inches, you’ve got politicians in Washington saying, ‘Huh, the National Weather Service – what’s their funding?’” he said.

Ramey said many forecasters are haunted by missed predictions. Wildfires and rain storms can be tricky to predict, he said, but “it’s the winter storms that really keep you up at night.”

Hubris

In our mythologies, weather is the ultimate metaphor for gods’ power. In Leviticus, the Hebrew God rewards the faithful by ending drought; elsewhere, he smites humanity with floods, fire, pestilence, “with thunder, and with earthquake, and great noise, with storm and tempest, and the flame of devouring fire.”

Indeed, in Greek mythology, humans’ original sin was trying to control weather: After Prometheus pilfers Zeus’ lightning bolt, the gods bind him to a rock for all eternity – and send an eagle to feast on his liver every day.

At the Weather Service in Grand Junction, forecasters chase Prometheus’ ambition, deploying technology and methodically assessing the data to empower mankind.

But until human knowledge is complete, even the most empirically minded scientists must fear God’s wrath.

“The weather event I’m most scared of is lightning. It’s the most common,” Pringle said. “Weather prediction has gotten so accurate that when you’re driving, you can usually predict whether there will be a flash flood or an avalanche and plan what to do.

“But you can’t plan the split second that lightning is going to come out of the sky. Boom!” he said.

Wresting a forecast from chaos

STEVE LEWIS/Durango Herald

Twice a day, the National Weather Service in Grand Junction launches helium balloons to an altitude of around 20,000 feet to gather data for forecasts, says Becky Klenk, a hydrometeorologist. The information harvested by the balloons is then fed into computer models.

STEVE LEWIS/Durango Herald

Jim Pringle, the warning coordination meteorologist with the National Weather Service in Grand Junction, said the Doppler radar atop Grand Mesa covers an area of 52,000 square miles. Because of Durango’s distance from the radar, the radar only picks up weather several miles above the city, Pringle said. “It’s just simply a range limitation,” he said.

STEVE LEWIS/Durango Herald

Jim Pringle, left, the warning coordination meteorologist with the National Weather Service, and forecasters Paul Frisbie, center, and Ellen Heffernan use computer modeling to make thousands of forecasts a day.

STEVE LEWIS/Durango Herald

Becky Klenk, a hydrometeorologist with the warning and forecast office in Grand Junction, said the office releases a weather balloon twice a day in conjunction with weather offices all over the world, to measure temperature, relative humidity, barometric pressure, wind speed, and wind direction. Klenk holds the instrument package that is launched twice daily.